Inserting implicit sequence points into computer program code to support debug operations

ABSTRACT

Arrangements described herein relate to inserting implicit sequence points into computer program code to support debug operations. Optimization of the computer program code can be performed during compilation of the computer program code and, during the optimization, implicit sequence points can be inserted into the computer program code. The implicit sequence points can be configured to provide virtual reads of symbols contained in the computer program code when the implicit sequence points are reached during execution of the computer program code during a debug operation performed on the computer program code after the computer program code is optimized and compiled.

BACKGROUND

An optimizing compiler is a compiler configured to optimize attributesof an executable computer program code to achieve a particular goal. Oneoptimization technique commonly implemented is to optimize a computerprogram to minimize the amount of time it takes to execute the computerprogram during operation. Another optimization technique commonlyimplemented is to minimize the amount of memory utilized by the computerprogram during operation.

There are several levels of optimization that a user can specify whencompiling a computer program. For example, the GNU Compiler Collection(GCC) specifies a number optimization levels. With level 0 (o0), nooptimization is performed. With level 1 (o1) optimization, most commonforms of optimization that do not require any speed-space tradeoffs areimplemented. Accordingly, the executable typically does not increase insize. With level 2 (o2) optimization, in addition to the optimizationsused in level 1, further optimizations are implemented, includinginstruction scheduling. Again, the executable typically does notincrease in size when level 2 optimization is used. With level 3 (o3)optimization, in addition to the optimizations used in level 1 and level2, more expensive optimizations (in terms of memory usage), such asfunction inlining, are used. Level 3 optimization may increase the speedof the resulting executable, but also may increase its size. Under somecircumstances, for example where these optimizations are not favorable,level 3 optimization may actually cause a program to execute slower.Other optimizations, such as loop-unrolling and size reductionoptimizations sometimes also are used.

BRIEF SUMMARY

One or more embodiments disclosed within this specification relate toinserting implicit sequence points into computer program code to supportdebug operations.

One embodiment can include a method of inserting implicit sequencepoints into computer program code to support debug operations. Themethod can include performing, using a processor, optimization of thecomputer program code during compilation of the computer program codeand, during the optimization, inserting implicit sequence points intothe computer program code. The implicit sequence points are configuredto provide virtual reads of symbols contained in the computer programcode when the implicit sequence points are reached during execution ofthe computer program code during a debug operation performed on thecomputer program code after the computer program code is optimized andcompiled. A view of a user program can remain valid by constraining theoptimization using implicitly generated virtual reads of user visiblesymbols at the implicit sequence points. When a debugger stops at atleast one of the implicit sequence points, user visible symbols can holdrespective values in a same manner the user visible symbols would holdthe respective values without optimization being performed on thecomputer program code.

Another embodiment can include a system including a processor programmedto initiate executable operations. The executable operations can includeperforming optimization of the computer program code during compilationof the computer program code and, during the optimization, insertingimplicit sequence points into the computer program code. The implicitsequence points are configured to provide virtual reads of symbolscontained in the computer program code when the implicit sequence pointsare reached during execution of the computer program code during a debugoperation performed on the computer program code after the computerprogram code is optimized and compiled. A view of a user program canremain valid by constraining the optimization using implicitly generatedvirtual reads of user visible symbols at the implicit sequence points.When a debugger stops at at least one of the implicit sequence points,user visible symbols can hold respective values in a same manner theuser visible symbols would hold the respective values withoutoptimization being performed on the computer program code.

Another embodiment can include a computer program product for insertingimplicit sequence points into first computer program code to supportdebug operations. The computer program product can include a computerreadable storage medium having second computer program code storedthereon, the second computer program code executable by a processor toperform a method. The method can include performing, by the processor,optimization of the computer program code during compilation of thecomputer program code and, during the optimization, inserting implicitsequence points into the computer program code. The implicit sequencepoints are configured to provide virtual reads of symbols contained inthe computer program code when the implicit sequence points are reachedduring execution of the computer program code during a debug operationperformed on the computer program code after the computer program codeis optimized and compiled.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a system for inserting implicitsequence points into computer program code in accordance with oneembodiment disclosed within this specification.

FIG. 2 presents an example of a portion of computer program code inwhich implicit sequence points can be inserted into the computer programcode.

FIG. 3 presents another example of a portion of computer program code inwhich implicit sequence points can be inserted into the computer programcode.

FIG. 4 presents another example of a portion of computer program code inwhich implicit sequence points can be inserted into the computer programcode.

FIG. 5 is a flow chart illustrating a method of inserting implicitsequence points into computer program code in accordance with anotherembodiment disclosed within this specification.

FIG. 6 is a block diagram illustrating a system for inserting implicitsequence points into computer program code in accordance with anotherembodiment disclosed within this specification.

DETAILED DESCRIPTION

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer-readablemedium(s) having computer-readable program code embodied, e.g., stored,thereon.

Any combination of one or more computer-readable medium(s) may beutilized. The computer-readable medium may be a computer-readable signalmedium or a computer-readable storage medium. A computer-readablestorage medium may be, for example, but is not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus, or device, or any suitable combinationof the foregoing. More specific examples (a non-exhaustive list) of thecomputer-readable storage medium would include the following: anelectrical connection having one or more wires, a portable computerdiskette, a hard disk drive (HDD), a solid state drive (SSD), a randomaccess memory (RAM), a read-only memory (ROM), an erasable programmableread-only memory (EPROM or Flash memory), an optical fiber, a portablecompact disc read-only memory (CD-ROM), a digital versatile disc (DVD),an optical storage device, a magnetic storage device, or any suitablecombination of the foregoing. In the context of this document, acomputer-readable storage medium may be any tangible medium that cancontain, or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

A computer-readable signal medium may include a propagated data signalwith computer-readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer-readable signal medium may be any computer-readable medium thatis not a computer-readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer-readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber, cable, RF, etc., or any suitable combination ofthe foregoing. Computer program code for carrying out operations foraspects of the present invention may be written in any combination ofone or more programming languages, including an object orientedprogramming language such as Java™, Smalltalk, C++ or the like andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The program codemay execute entirely on the user's computer, partly on the user'scomputer, as a stand-alone software package, partly on the user'scomputer and partly on a remote computer, or entirely on the remotecomputer or server. In the latter scenario, the remote computer may beconnected to the user's computer through any type of network, includinga local area network (LAN) or a wide area network (WAN), or theconnection may be made to an external computer (for example, through theInternet using an Internet Service Provider).

Aspects of the present invention are described below with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer, other programmable data processing apparatus,or other devices create means for implementing the functions/actsspecified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in acomputer-readable medium that can direct a computer, other programmabledata processing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer-readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

For purposes of simplicity and clarity of illustration, elements shownin the figures have not necessarily been drawn to scale. For example,the dimensions of some of the elements may be exaggerated relative toother elements for clarity. Further, where considered appropriate,reference numbers are repeated among the figures to indicatecorresponding, analogous, or like features.

Arrangements described herein relate to inserting implicit sequencepoints into computer program code to support debug operations.Typically, in order to debug a computer program, the computer program iscompiled without optimization. When a computer program is compiled withoptimization, the optimized computer program code may not maintain thesequential execution of the original source code and machine state atany point in the original source code may not be well defined. Thepresent arrangements are directed to the insertion of implicit sequencepoints into computer program code in a manner that supports debugoperations on compiled computer program code while retaining at leastmost of the runtime performance improvements of optimization technology.As used herein, the term “implicit sequence point” means a sequencepoint not explicitly defined by an operating language in which computerprogram code is written.

By providing the computer program both with debug support andoptimization in accordance with the present arrangements, users quicklymay be able to find regions of transformed code that cause failures orerrors during execution of the compiled computer program code. Further,the compiled computer program code typically may achieve at least70%-80% of the runtime performance of level 2 (o2) optimization for C,C++ and Fortran Spec2006 benchmarks, while retaining a valid view of thecomputer program in a debugger at the set of sequence points.

FIG. 1 is a block diagram illustrating a system 100 for insertingimplicit sequence points into computer program code 110 in accordancewith one embodiment disclosed within this specification. The system caninclude a compiler 120 that receives the computer program code 110 assource code, and compiles the computer program code 110 to transform thecomputer program code 110 from a programming language to a targetlanguage to generate compiled computer program code 130 (e.g., objectcode), and thus create an executable program from the computer programcode 110. During compilation, the compiler 120, for example using anoptimizer 125, can perform at least one level of optimization on thecomputer program code 110. For example, the compiler 120 can optimizethe computer program code 110 to reduce an amount of time required toexecute the compiled computer program code 130 and/or optimize thecomputer program code 110 to reduce an amount of memory utilized by thecompiled computer program code 130 at run time. As noted, however, thereare several levels of optimization that can be performed on the computerprogram code 110, and the invention is not limited in this regard.

During optimization, the compiler 120 (e.g., using the optimizer 125)can insert into the computer program code 110 implicit sequence points.The implicit sequence points can be configured to provide virtual readsof symbols contained in the compiled computer program code 130 whenrequested. As used herein, the term “virtual read” means anidentification of where a value for a symbol is stored in memory. Forexample, when the implicit sequence points are reached during executionof the compiled computer program code 130 during a debug operationperformed on the compiled computer program code 130, the debugger canrequest the values of symbols corresponding to the sequence point. Sincethe memory location where the values of the symbols is known via thevirtual reads, the values can be accessed and presented to a user, forexample via the debugger.

The implicit sequence points can be inserted into the computer programcode 110 at locations in the computer program code 110 where it isdesired that a view of the computer program remain valid. To ensure theview remains valid, when the computer program code 110 is compiled, thecompiler 120 can translate the implicit sequence points and model theimplicit sequence points as virtual reads of the user visible symbols atthe implicit sequence points. In this regard, the compiler 120 can beconstrained from performing undesired transformations of the computerprogram code 110 to ensure user visible symbols retain correct values atthe implicit sequence points, for example using processes otherwise usedto retain correct program semantics.

The implicit sequence points further can provide virtual reads ofindirect operations performed by the computer program code 110 (i.e.,during execution of the compiled computer program code 130). Theindirect operations can be operations that process one or more variablesnot specifically assigned in the computer program code 110. For example,in addition to reading user visible symbols, the implicit sequencepoints can provide virtual reads of indirect operations (e.g., shadowsymbols) used by the computer program code 110. The values of the shadowsymbols can be accessed through identification of pointers which pointto named and/or unnamed symbols/variables. For example, the valuesstored at a memory locations identified by the pointers can be read. Inone arrangement, one or more of the implicit sequence points can readnot only values for user visible symbols and/or shadow symbolscorresponding to the place in the computer program code 110 where theimplicit sequence points are placed, but also values for other symbolsand/or shadow symbols used in the computer program code 110. Readingsuch other symbols can simplify a debug analysis performed on thecompiled computer program code 130.

Further, a list of symbols to be referenced by virtual reads can beprovided for one or more of the implicit sequence points. Indeed, aunique symbol set can be provided for each of the implicit sequencepoints, and the implicit sequence points can be modeled as virtual readsof the listed symbols/shadow symbols. Thus, not all symbols/shadowsymbols need be handled as if they were to be read. Instead, implicitsequence points need only be provided for the listed symbols/shadowsymbols. This can reduce the memory consumption used by the compiledcomputer program code 130 when executed, as well as reduce executiontime.

In one arrangement, the locations where the implicit sequence points areinserted into the computer program code 110 can be specified by a user,for example in response to a user input received via the compiler 120specifying compile options for the computer program code 110. Such userinput can be received via a user interface 135 provided for the compiler120, or another suitable user interface. In another arrangement, thelocations where the implicit sequence points are inserted can bedetermined by one or more policies and, for example, may be controlledthrough user selectable compiler options. For example, implicit sequencepoints can be inserted at the beginning of each user statement in thecomputer program code 110.

In a further arrangement, the compiler 120 can automatically determine,based on one or more policies, locations in the computer program code110 where a user would want (or likely would want) the implicit sequencepoints to be placed into the computer program code based on a userexperience provided by the computer program code 110, and automaticallyinsert the implicit sequence points at those locations. For example, ifthe computer program code 110 performs a calculation on parameter valuesthat affect the user experience, an implicit sequence point can beinserted into the computer program code 110 at the beginning ofstatement which performs the calculation. The number of implicitsequence points inserted into the computer program code 110 can be aselected value within a predetermined range of values, though this neednot be the case. For example, the user can be presented thepredetermined range of values and prompted to select one of the values.

When the debug operation is performed on the compiled computer programcode 130, a debugger can stop execution on the compiled computer programcode 130, at least temporarily, at each implicit sequence point. In thisregard, each implicit sequence point can indicate a point in thecompiled computer program code 130 where execution is to be stopped, atleast temporarily, during debug operations. When the debugger stops at asequence point, user visible symbols and/or shadow symbols hold therespective values in a same manner the user visible symbols and shadowsymbols would hold the respective values without optimization beingperformed on the computer program code 110, and the symbols can beviewed by a user (e.g., debugger can present such values to the user).

Further, the compiled computer program code 130 can be configured toenable user modification of one or more values of the symbols during thedebug operation, for example by making a virtual read also a virtualwrite into a virtual data store. In this regard, the compiler 120 canimplicitly insert virtual writes to user visible symbols betweenimplicit sequence points so that optimization of the computer programcode 110 includes providing in the compiled computer program code 130the ability for a user to modify one or more symbols in the compiledcomputer program code 130, via the debugger, wherein such ability is notprovided in the computer program code 110. Thus, when execution of thecompiled computer program code 130 stops at a particular implicitsequence point, the values of symbols can be presented to a user, andthe user can be provided the opportunity to modify one or more suchvalues in the compiled computer program code 130 during the debugoperation. Execution of the compiled computer program code 130 can againcommence from that implicit sequence point in response to the debuggerreceiving a user input indicating to the debugger to continue execution.

In view of the foregoing, the present arrangements provide a problemdetermination technique that can aid the investigation of applicationfailures when the computer program code 110 is compiled, withoptimization, into the computer program code 130.

FIG. 2 presents an example of a portion 200 of computer program code 110in which implicit sequence points can be inserted into the computerprogram code 110. User visible symbols can be chosen by the compiler(e.g., via a language translator) based on the rules of the specificprogramming language being compiled. For indirect operations, existingside effect information that is generated by the compiler can be used tosupport optimization. For instance, in this example, “*p” effectivelycan be a symbol that represents the set of all symbols that potentiallycan be accesses through a pointer “p.” The contents of that set can becomputed by the compiler. In one arrangement, “*p” can be nativelydefined to represent all symbols in the computer program code, or aliasrefinement techniques can be used to refine the set “*p” for eachimplicit sequence point.

When the computer program code 110 is compiled, implicit sequence pointscan be inserted at the beginning of each of the statements 210, 220,230. In this example, a sequence point inserted at the beginning of thestatement 210 can provide virtual reads of the symbols “g”, “a”, “b”,“p” and “*p”. At this sequence point, “c” would not be visible to theuser. A sequence point inserted at the beginning of the statement 220can provide virtual reads of the symbols “g”, “a”, “b”, “c”, “p” and“*p”. A sequence point inserted at the beginning of the statement 230also can provide virtual reads of the symbols “g”, “a”, “b”, “c”, “p”and “*p”.

FIG. 2 presents an example of a portion 200 of computer program code inwhich implicit sequence points can be inserted into the computer programcode. User visible symbols can be chosen by the compiler (e.g., via alanguage translator) based on the rules of the specific programminglanguage being compiled. For indirect operations, existing side effectinformation that is generated by the compiler can be used to supportoptimization. For instance, in this example, “*p” effectively can be asymbol that represents the set of all symbols that potentially can beaccesses through a pointer “p.” The contents of that set can be computedby the compiler. In one arrangement, “*p” can be natively defined torepresent all symbols in the computer program code, or alias refinementtechniques can be used to refine the set “*p” for each implicit sequencepoint.

When the computer program code is compiled, implicit sequence points canbe inserted at the beginning of each of the statements 210, 220, 230. Inthis example, a sequence point inserted at the beginning of thestatement 210 can provide virtual reads of the symbols “g”, “a”, “b”,“p” and “*p”. At this sequence point, “c” would not be visible to theuser. A sequence point inserted at the beginning of the statement 220can provide virtual reads of the symbols “g”, “a”, “b”, “c”, “p” and“*p”. A sequence point inserted at the beginning of the statement 230also can provide virtual reads of the symbols “g”, “a”, “b”, “c”, “p”and “*p”. Notwithstanding, a list of symbols that are to be read at eachsequence point can be provided to pessimize the set of symbols (e.g.,reduce the number of symbols that are read) in order to reduce memoryconsumption used during execution of the compiled computer program code.For example, C and C++ implementations can provide unique symbol setsfor the implicit sequence points on a per function basis. As noted, thecompiler (e.g., via the optimizer) can translate the implicit sequencepoints and model them as virtual reads of the listed symbols.

FIG. 3 presents another example of a portion 300 of computer programcode in which implicit sequence points can be inserted into the computerprogram code. If conventional optimization were enabled duringcompilation and applied to this portion 300 of computer program code,the statement 310 storing the value “5” to the symbol “i”, and thestatement returning the square of “i” typically would be removed. Hence,the value “5” would not be stored to the symbol “i” in a compiledversion of the computer program code. Instead, conventional optimizationwould store a value of 25 for the symbol “foo”. In accordance with thepresent arrangements, however, by inserting an implicit sequence pointat the beginning of the statement 310, a virtual read of the value “5”for the symbol “i” will be performed during a debug operation performedon the computer program code. Performance of the resulting executablemight be slower at the benefit of materializing the store of the value“5” to the symbol “i”, but debugging of the computer program will befacilitated.

If an implicit sequence point is inserted at the beginning of thestatement 320, the square operation can be preserved as well. If not,the square operation can be inlined into the statement 330 by replacing“5*5” with the value “25” at compile time, and statement 330 can beremoved, thereby still providing a level of optimization to the portion300 of computer program code.

FIG. 4 presents another example of a portion 400 of computer programcode in which implicit sequence points can be inserted into the computerprogram code. In this example the common sub expression “x*y” instatements 410, 420 can be identified. To avoid calculating “x*y” twotimes, during optimization a shadow variable can be assigned to thevalue “x*y”, and this shadow variable can be used in the statements 410,420. Moreover, part of the index calculation of the array “a” can bereused to deduce the outcome of the conditional statement 430. Anycompiler internal variables also can be optimized. Accordingly, theconditional statement “2>t1” need not be evaluated at compile time.Nonetheless, the values of symbols “t1”, “t2”, “q” and “z”, still can bestored to memory when they are calculated, making them available to adebug operation when one or more suitable implicit sequence points areplaced in the portion 400 of the computer program code, for example atthe beginning of statements 410, 420 and 450.

FIG. 5 is a flow chart illustrating a method 500 of inserting implicitsequence points into computer program code in accordance with anotherembodiment disclosed within this specification. At step 505, compilationand optimization of computer program code can be initiated. For example,a user can initiate compilation via a user interface of a compiler, andselect one or more options to optimize the computer program code.Further, the user can choose to have implicit sequence points insertedinto the computer program code during compilation/optimization.

At step 510, a determination can be made where the implicit sequencepoints are to be inserted into the computer program code. For example,one or more user inputs can be received specifying where to insert theimplicit sequence points, or the compiler can automatically choose whereto insert the implicit sequence points, for example as previouslydescribed.

At step 515, during compilation and optimization of the computer programcode, the implicit sequence points can be inserted into the computerprogram code, for example at the determined locations. The implicitsequence points can be configured to provide virtual reads of symbolscontained in the computer program code when the implicit sequence pointsare reached during execution of the computer program code during a debugoperation performed on the computer program code after the computerprogram code is optimized and compiled.

At step 520, the compiled and optimized computer program code can beoutput. If a user so chooses, the user can execute the compiled computerprogram code using a debugging application. During the debug operation,execution of the program code can be stopped, at least temporarily, ateach of the implicit sequence points, and the implicit sequence pointscan provide virtual reads of symbols contained in the computer programcode.

FIG. 6 is a block diagram illustrating a processing system 600 forinserting implicit sequence points into computer program code inaccordance with another embodiment disclosed within this specification.The processing system 600 can include at least one processor 605 (e.g.,a central processing unit) coupled to memory elements 610 through asystem bus 615 or other suitable circuitry. As such, the processingsystem 600 can store program code within the memory elements 610. Theprocessor 605 can execute the program code accessed from the memoryelements 610 via the system bus 615. It should be appreciated that theprocessing system 600 can be implemented in the form of any systemincluding a processor and memory that is capable of performing thefunctions and/or operations described within this specification. Forexample, the processing system 600 can be implemented as a computer(e.g., a desktop computer, a laptop computer, a tablet computer, aworkstation, a server, etc.)

The memory elements 610 can include one or more physical memory devicessuch as, for example, local memory 620 and one or more bulk storagedevices 625. Local memory 620 refers to RAM or other non-persistentmemory device(s) generally used during actual execution of the programcode. The bulk storage device(s) 625 can be implemented as a hard diskdrive (HDD), solid state drive (SSD), or other persistent data storagedevice. The processing system 600 also can include one or more cachememories (not shown) that provide temporary storage of at least someprogram code in order to reduce the number of times program code must beretrieved from the bulk storage device 625 during execution.

Input/output (I/O) devices such as a display 630, a pointing device 635and, optionally, a keyboard 640 can be coupled to the processing system600. The I/O devices can be coupled to the processing system 600 eitherdirectly or through intervening I/O controllers. For example, thedisplay 630 can be coupled to the processing system 600 via a graphicsprocessing unit (GPU), which may be a component of the processor 605 ora discrete device. One or more network adapters 645 also can be coupledto processing system 600 to enable processing system 600 to becomecoupled to other systems, computer systems, remote printers, and/orremote storage devices through intervening private or public networks.Modems, cable modems, transceivers, and Ethernet cards are examples ofdifferent types of network adapters 645 that can be used with processingsystem 600.

As pictured in FIG. 6, the memory elements 610 can store the componentsof the system 100 of FIG. 1, namely the compiler 120, optimizer 125 andthe user interface 135. Being implemented in the form of executableprogram code, these components of the system 100 can be executed by theprocessing system 600 and, as such, can be considered part of theprocessing system 600. Moreover, the compiler 120, optimizer 125 and theuser interface 135 are functional data structures that impartfunctionality when employed as part of the processing system of FIG. 6.Optionally, the memory elements 610 can store the computer program code110 and, once the computer program code 110 is compiled, the compiledcomputer program code 130. The computer program code 110 and compiledcomputer program code 130 also may be stored elsewhere, for example onanother system to which the processing system 600 is communicativelylinked, for example via the network adapter(s) 645.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “includes,”“including,” “comprises,” and/or “comprising,” when used in thisspecification, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment disclosed within thisspecification. Thus, appearances of the phrases “in one embodiment,” “inan embodiment,” and similar language throughout this specification may,but do not necessarily, all refer to the same embodiment.

The term “plurality,” as used herein, is defined as two or more thantwo. The term “another,” as used herein, is defined as at least a secondor more. The term “coupled,” as used herein, is defined as connected,whether directly without any intervening elements or indirectly with oneor more intervening elements, unless otherwise indicated. Two elementsalso can be coupled mechanically, electrically, or communicativelylinked through a communication channel, pathway, network, or system. Theterm “and/or” as used herein refers to and encompasses any and allpossible combinations of one or more of the associated listed items. Itwill also be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms, as these terms are only used to distinguishone element from another unless stated otherwise or the contextindicates otherwise.

The term “if” may be construed to mean “when” or “upon” or “in responseto determining” or “in response to detecting,” depending on the context.Similarly, the phrase “if it is determined” or “if [a stated conditionor event] is detected” may be construed to mean “upon determining” or“in response to determining” or “upon detecting [the stated condition orevent]” or “in response to detecting [the stated condition or event],”depending on the context.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the embodiments disclosed within this specification havebeen presented for purposes of illustration and description, but are notintended to be exhaustive or limited to the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of theembodiments of the invention. The embodiments were chosen and describedin order to best explain the principles of the invention and thepractical application, and to enable others of ordinary skill in the artto understand the inventive arrangements for various embodiments withvarious modifications as are suited to the particular use contemplated.

What is claimed is:
 1. A method of inserting implicit sequence pointsinto computer program code to support debug operations, the methodcomprising: performing, using a processor, optimization of the computerprogram code during compilation of the computer program code and, duringthe optimization, inserting implicit sequence points into the computerprogram code, wherein the implicit sequence points are configured toprovide virtual reads of symbols contained in the computer program codewhen the implicit sequence points are reached during execution of thecomputer program code during a debug operation performed on the computerprogram code after the computer program code is optimized and compiled,wherein a view of a user program remains valid by constraining theoptimization using implicitly generated virtual reads of user visiblesymbols at the implicit sequence points and wherein, when a debuggerstops at at least one of the implicit sequence points, user visiblesymbols hold respective values in a same manner the user visible symbolswould hold the respective values without optimization being performed onthe computer program code.
 2. The method of claim 1, further comprising:during the compilation of the computer program code, automaticallydetermining locations in the computer program code where a user wouldwant the implicit sequence points to be inserted into the computerprogram code based on a user experience provided by the computer programcode, wherein inserting the implicit sequence points into the computerprogram code comprises inserting the implicit sequence points at theautomatically determined locations.
 3. The method of claim 1, whereinthe implicit sequence points further provide virtual reads of indirectoperations performed by the computer program code during execution ofthe computer program code, the indirect operations pertaining tooperations that process at least one variable not specifically assignedin the computer program code.
 4. The method of claim 1, whereinperforming optimization of the computer program code comprisesperforming at least one level of optimization, the level of optimizationselected from a group consisting of optimizing the computer program codeto reduce an amount of time required to execute the computer programcode and optimizing the computer program code to reduce an amount ofmemory utilized by the computer program code during operation.
 5. Themethod of claim 1, wherein the implicit sequence points indicate pointsin the computer program code where execution is to be stopped, at leasttemporarily, during the debug operation.
 6. The method of claim 1,wherein a number of the implicit sequence points inserted into thecomputer program code is a selected value within a predetermined rangeof values.
 7. The method of claim 1, further comprising: specifying aplurality of locations where the implicit sequence points are to beinserted into the computer program code in response to a user inputreceived via a compiler configured to compile the computer program code;wherein inserting implicit sequence points into the computer programcode comprises inserting the implicit sequence points at the pluralityof locations.